A STUDY OF THE DILATION OF THE UNIT-CELL OF METALLOCENE ISOTACTIC POLY(PROPYLENES) - THE MONOCLINIC FORM

The lattice parameters of a series of monoclinic metallocene poly(prop ylenes) of constant molecular weight are measured as a function of def ect content, that vary between 0.3 and 2.35 total defects per 100 mono meric units. The parameters are also measured as a function of molecul ar weight for a fixed defect content and as a function of the crystall ization temperature. The b axis is found to increase with decreasing i sothermal crystallization temperature whereas only small changes are f ound for samples rapidly crystallized. The a and c axis showed basical ly no variation with crystallization temperature. The parameters of th e unit cell were essentially constant with varying defect content in t he poly(propylene) chain. Lack of observed effect on the dilation of t he unit cell by increasing defects is a consequence of the rapid cryst allization required to ensure formation of monoclinic crystals. The un it cell parameters increased as a mild function of the molecular weigh t. (C) 1997 John Wiley & Sons, Inc.